Methods of coating pipe

ABSTRACT

A method is provided for forming an electrically insulative pipe by the steps of assembling an elongated wrapper having an inner band of self-adhering adhesive and an outer band of a mechanically strong material and wrapping said wrapper about a pipe to be protected with one side edge being bent upon itself so as to form an exposed edge of adhesive engaging the adhesive on the opposite edges of the wrap whereby to form an adhesive-toadhesive bond at the overlap.

United States Patent [72] Inventor John H. Royston Pittsburgh, Pa. [21]App1.No. 881,365 [22] Filed Dec. 2, 1969 [45] Patented Sept. 21, 1971[73] Assignee Royston Laboratories, Inc.

[54] METHODS OF COATING PIPE 5 Claims, 2 Drawlng Figs.

[52] US. Cl 156/187, 156/195,156/392 [51] Int. Cl 1165b 81/03 [50] Field01 Search 156/184. 187, 195, 392

[56] References Cited UNITED STATES PATENTS 2,874,722 2/1959 l-lamblin156/195 X 3,024,153 3/1962 Kennedy 156/195 X 3,033,724 5/1962 Stokes156/184 X 3,063,833 11/1962 Howard et al. 156/187 3,189,052 6/1965Devaney 156/184 X 3,195,427 7/1965 Adams 156/195 X 3,338,270 8/1967Denenberg 156/184 X Primary Examiner-Benjamin R. Padgett AssistantExaminer-Gary G. Solyst A!!0rney-Buell, Blenko & Ziensenheim ABSTRACT: Amethod is provided for forming an electrically insulative pipe by thesteps of assembling an elongated wrapper having an inner band ofself-adhering adhesive and an outer band of a mechanically strongmaterial and wrapping said wrapper about a pipe to be protected with oneside edge being bent upon itself so as to form an exposed edge ofadhesive engaging the adhesive on the opposite edges of the wrap wherebyto form an adhesive-to-adhesive bond at the overlap.

PATENTED SEP21 IHYI 3.607.516

INVEN'I'OR John H. Royston This invention relates to methods of coatingpipe and particularly to a method of coating pipe using a tape having aselfadhesive, self-sealing or pressure-sensitive layer.

The coating of pipe to provide protection against corrosion particularlyby electrolyte process is old and well known. Wrappers of various kindshave been applied over painted coatings of asphalts and like materialsfor many years. So also have coatings of pressure-sensitive and liketapes been applied directly to the metallic pipe surface. Unfortunatelythe resultant coatings have not been entirely satisfactory for a varietyof reasons. In the application of tape over a painted coating there areproblems of maintaining uniformity of coating thickness as well asintegrity of the total coating. Moreover such coatings require a two ormore stage application of the several layers making up the coating witha variety of specialized equipment for the application. In the case ofpressuresensitive and like tapes, the problem is primarily lack ofintegrity of the coating and resultant leakage at the overlapped joints.Experience has shown and logic reasons that pressuresensitive tapeswhich can be unrolled from their coils by readily unwinding, do notpossess sufi'icient bonding strength between the pressure-sensitiveadhesive and the backing of the tape or it would not unroll. Apressure-sensitive tape that can be so easily unrolled will possess nogreater ability to bond to its own backing at the overlap when appliedto the pipe, and therefore, will not provide a sufficient watertightseal at the overlap area, thus permitting moisture to enter under theinsulation at this point.

I have found a method of overcoming these problems of the prior artmethods and at the same time providing a raised protective rib whichprotects the coating from damage while the pipe is being handled andcovered.

Preferably lform an electrically insulative wrapped pipe by the steps ofassembling an elongated wrapper having an inner band of a self-adheringadhesive material and an outer band of a mechanically strong material,wrapping said elongated wrapper about a pipe to be coated with one sideedge being bent back upon itself so as to form an exposed edge ofadhesive engaging the adhesive on the opposite edge of the wrap wherebyto form an adhesive to adhesive bond at the overlap of such wrap. Thetension will be increased at the lap area due to the increasedthickness, thus affecting a greater fusion of the pressure-sensitive orself-sealing adhesive within the fold. By turning back the fold thepossibility of moisture seeping in at the overlap is eliminated.Preferably the wrap is applied in helical form so as to form acontinuous helical rib extending around the pipe from end to end. Byactual tests using a Dillon Universal Testing Machine, one typical gradeof pressure-sensitive pipeline tape identified as No. 43, manufacturedby Minnesota Mining & Manufacturing Company, it can be seen that thebond strength of adhesive to adhesive is three times greater than thebond strength between the adhesive and the backing of this tape. Thistest was conducted by using -inch strips of tape as follows: l Place thepressure-sensitive adhesive side of two strips face to face for a totalof 3 inches in length, leaving two of the 2-inch ends unattached. Placethese 2-inch tabs in the jaws of the Dillon Universal Testing Machineand record the pounds pull required to separate the 3-inch area. (2)Place the pressure-sensitive adhesive side on one strip on the plasticback side of the second strip for a total of 3 inches in length, leaving2 of the 2-inch ends unattached. Place these 2-inch tabs in the jaws ofthe Dillon Universal Testing Machine and record the pounds pull requiredto separate the 3-inch area. When comparing self-sealing tapesmanufactured for pipeline use, products such as that manufactured byPlicoflex rely on the softness of their butyl vinyl sealant to squeezeout under pressure to affect a seal at the lap in an area approximatelyone-sixteenth of an inch as they obtain little or no bond of theadhesive to their PVC backing. But by my invention a product of thistype will have the advantage of extending the self-sealing area to asmuch as one-half inch and the bond between the two self-sealingl layerswill now be determined by the cohesive strength of t e compound. Theadhesive may be any of the pressure-sensitive and self-sealing materialsused in the present forms of pressure-sensitive and self-sealingwrappers. It may be for example natural rubber, styrene butadienerubber, butyl rubber, neoprene, nitrile rubber, polysulfide rubber,ethylene propylene copolymer or terpolymer and the like. The outer bandor layer is preferably a strong resilient material such as a film ofpolyvinyl chloride, polypropylene, cellulose acetate, polyolefins,polycarbonates, polyesters and the like material. The band or wrappermay be applied to a pipe or over a wet or dry primer.

In the foregoing general description of my invention 1 have set outcertain purposes, objects and advantages of my invention. Other objects,purposes and advantages of the invention will be apparent from aconsideration of the following description and the accompanying drawingsin which:

FIG. 1 is an isometric view of a pipe having a coating applied accordingto my invention,

FIG. 2 is a cross section of a coated pipe according to my invention.

Referring to the drawings I have illustrated a pipe 10 having appliedthereto a wrapper made up of a band 11 of polyethylene having a layer 12of adhesive elastomer on one side thereof. One edge 13 of the wrapper isturned over upon itself as it is applied to the pipe 10 so that anexposed face of adhesive 12 engages the adhesive layer 12 of theopposite edge 14 of the next succeeding wrap of the wrapper on the pipe.As the wrapper is drawn tight the adhesive layers flow together forminga complete seal and at the same time a helical rib 15 which extends fromone end of the pipe to the other and on which the pipe will rest,raising the balance of the coating away from the surface on which thepipe rests. This protects the pipe coating from abrasion and damagewhile eliminating the problem of leakage at the wrap joint whichoccurred in the past because the pressure sensitive layer contacted theouter wrap to which it was not adhesively bonded leaving a zone ofweakness.

In the foregoing specification I have set out a preferred practice of myinvention, however, it will be understood that this invention mayotherwise be embodied within the scope of the following claims.

Iclaim:

l. A method of forming an electrically insulative wrapped pipecomprising the steps of:

a. assembling an elongated wrapper having an inner band of aself-adhering adhesive material and an outer layer of a mechanicallystrong material, said wrapper having spaced apart generally parallelside edges, and

. wrapping said elongated wrapper about a pipe to be protected with theadhesive inner band contacting said pipe, and one side edge of saidwrapper bent back upon itself so as to form an exposed edge of adhesiveengaging the adhesive on the opposite edge of the wrapper whereby toform an adhesive to adhesive band at the overlap of said wrap.

2. A method as claimed in claim 1 wherein the wrapper is appliedhelically about the pipe and the overlap of each succeeding wrap forms ahelical rib from one end of the pipe to the other.

3. A method as claimed in claim 1 wherein the pipe is coated with aprimer prior to wrapping.

4. A method as claimed in claim 1 wherein the outer layer is a memberfrom the group consisting of ethylene-vinyl acetate, polypropylene,polyvinyl chloride, polycarbonates, cellulose acetate, cellulosebutyrate, polyesters, polystyrene, polyethylene copolymer andpolyolefins.

5. A method as claimed in claim 1 wherein the inner layer is -a memberfrom the group consisting of natural rubber, styrene butadiene rubber,butyl rubber, neoprene, nitrile rubber, ethylene propylene copolymer orterpolymer, polyvinyl chloride and polysulfide rubber.

2. A method as claimed in claim 1 wherein the wrapper is appliedhelically about the pipe and the overlap of each succeeding wrap forms ahelical rib from one end of the pipe to the other.
 3. A method asclaimed in claim 1 wherein the pipe is coated with a primer prior towrapping.
 4. A method as claimed in claim 1 wherein the outer layer is amember from the group consisting of ethylene-vinyl acetate,polypropylene, polyvinyl chloride, polycarbonates, cellulose acetate,cellulose butyrate, polyesters, polystyrene, polyethylene copolymer andpolyolefins.
 5. A method as claimed in claim 1 wherein the inner layeris a member from the group consisting of natural rubber, styrenebutadiene rubber, butyl rubber, neoprene, nitrile rubber, ethylenepropylene copolymer or terpolymer, polyvinyl chloride and polysulfiderubber.